In cases of discospondylitis, changes in the intervertebral disk space are observed, and the vertebral end plates exhibit
symmetrical lysis and the vertebral bodies exhibit sclerosis.2,4 There is generally about a two- to four-week lag time in the onset of clinical signs of discospondylitis and the first radiographic
evidence.6,36 In addition, radiographic changes during recovery lag behind clinical improvement. A study of radiographic changes during
recovery from discospondylitis showed that in older dogs, this lag period may be three to nine weeks, while it is shorter
in dogs under 1 year of age.36 Since vertebral physitis is a disease similar to discospondylitis, these lag times in radiographic changes should be taken
into consideration when interpreting initial and follow-up radiographs in dogs with vertebral physitis.
Other imaging study findings
Other diagnostic imaging studies can be used in evaluating vertebral infections. Myelography may show evidence of extradural
compression, such as attenuation of the contrast medium column in the subarachnoid space over the affected disk space or vertebra.
Computed tomography can identify bone pathology and paravertebral soft tissue swelling.4,37 Magnetic resonance imaging (MRI) is the diagnostic procedure of choice to identify infected vertebrae, especially in the
early stages of the disease process.4,32,37
4. A sagittal midline T2-weighted magnetic resonance image of the cervical region from an 11-year-old Weimaraner with intervertebral
disk disease. The degenerative disks are characterized by hypointensity of the nucleus pulposus (arrows).
MRI should be considered in cases in which radiographic imaging or computed tomography does not reveal distinct evidence of
a vertebral infection. With MRI, degenerative changes of the intervertebral disk are characterized by a loss of signal intensity
of the nucleus pulposus on T2-weighted images (Figure 4), while infection causes T2-weighted hyperintensity of both the nucleus pulposus and the anulus fibrosus (Figure 5).37
5. A sagittal midline T2-weighted magnetic resonance image of a 1.5-year-old greater Swiss mountain dog. There is an irregularly
marginated area of increased signal intensity centered at an intervertebral disk space in the midthoracic spine (arrow). At
this site, the normal smooth, linear, low signal pattern of the vertebral end plates has been lost, consistent with a destructive
process expanding outward from the intervertebral disk space. The adjacent bone of the vertebral bodies is expanded in dorsoventral
dimension and reduced in signal, consistent with remodeling and sclerosis. Reactive, irregular periosteal new bone is visible
bridging the ventral aspect of the disk space. These changes are consistent with chronic active infectious discospondylitis.
Fluoroscopic-guided percutaneous needle aspiration with cytologic examination and bacterial and fungal cultures are indicated
in dogs that do not respond to initial antibiotic therapy or if the diagnosis is unclear.4